Additives: Flame retardants at a crossroads

Flame retardants
(FRs) are
continuously being
improved to offer
consumers the best
choice to ensure
overall safety,
however, green
alternatives are
facing challenges,
says Angelica Buan
in this report.

If we had to choose between fire
safety or safety from health risks,
which would it be? Obviously, the
choice would be both.

Every day, we are in contact with
objects that are potentially flammable
or fire hazards, such as those made
from plastics, fabrics, wood and paper.
These materials could exacerbate
the fires coming from faulty wirings,
heating cooking appliances, lit candles,
smoking, and other causes. Flame
retardant additives, which have been in
use in many consumer and industrial
products since the 1970s, can help delay
their ignition.

According to market research firm
Ceresana, approximately 2.26 million
tonnes of flame retardants (FRs) were
processed worldwide in 2018.

The construction sector, a major
application accounting for 30% of global
demand, and the electrical industry,
accounting for 534,000 tonnes of the
global demand, represent the largest sales markets, Ceresana’s report said.

Other common applications of FRs are in furnishings (foam, mattresses, carpets,
curtains, and fabric blinds), transportation parts, such as seats, seat covers and fillings,
bumpers, and overhead compartments, and others.

It is for this reason that the FR market is projected to expand at a CAGR rate of 3.8%
from 2018-2025, and the growth in applications will expand to electric vehicles, smart
appliances, and novel consumer electronics, Frost & Sullivan furthered in its market
study.

Exposure to FRs has health risks, says study

A downside to chemical-based FRs is that the additives have been associated with severe
health conditions including endocrine and thyroid disruption, impact to the immune
system, reproductive toxicity, cancer, and adverse effects to foetal and child development
and neurologic function, according to a report from US-based National Institute of
Environmental Health Sciences.

Exposure comes through house dust, ingestion, and many other ways that are not
quite obvious, especially since humans can spread the substance through their hands,
adds the study. The chemicals can get into the air, water, and soil during manufacture.
Moreover, FRs are also reported to contribute to the toxicity of plastics.

The presence of FRs in many common products, from car seats to mobile gadgets to
pet accessories, is also raising concern among consumers.

A study carried out by the Indiana University in 2018 tested 18 children’s car seats
(and 36 different fabric and foam samples from the car seats) manufactured in the US,
Canada and China, between January 2017 and February 2018. It found that 15 seats
contained traditional and new FR replacements, such as the phosphonate esters that are
promoted as safer alternatives.

Children's car seats are required to meet the
flammability standards for car interiors outlined in
the Federal Motor Vehicle Safety Standard 302 of the
US National Highway Traffic Safety Administration.
However, FRs have been linked to a variety of negative
health effects, including hormone disruption, impaired
brain development, liver damage and cancer. Children
are more susceptible to these effects than adults because
of their smaller size and their tendency to put their hands
and objects in their mouths.

Exposure to FRs in car seats is through inhalation of
the chemicals that leach into the air out of fabrics and
foam; or by ingestion of the dust that accumulates inside
vehicles, through skin contact or by chewing on their car
seats.

The researchers claimed that while car seat
manufacturers are moving away from using certain toxic
chemicals compounds, they were not specific as to what
replacements were being used.

Meanwhile, widespread adoption of mobile phones
may also be a source of FR exposure, according to a study
by the University of Toronto.

It is the first study to identify hand-held electronic
devices as a potential source of exposure to
organophosphate esters, chemicals often used either as
FRs or plasticisers that make materials such as PVC more
flexible and durable. These chemicals, the researchers
said, have been linked to neurotoxicity, decreased fertility
and thyroid
problems.

The researchers found a connection between levels of
organophosphate esters on electronic devices and levels
on hands and in urine samples (of the study participants).
Further, they found that levels of FRs and plasticisers were
higher on hand-held devices, such as mobile phones and
tablets, than non-hand-held electronics, such as televisions
and desktop computers.

As such, handheld devices like mobile phones, may be
sources of some of these compounds, or may be indicators
of chemical exposure from other sources such as their
homes, cars and workplaces.

Not only humans but pets may be at risk of FR
exposure, according to another study. Published in
American Chemical Society (ACS)’s Environmental
Science & Technology journal, it associated the FR Tris
(1,3-dichloro-2-isopropyl) Phosphate (TDICPP) contained
in silicone tags to feline hyperthyroidism, the most
common endocrine-related disease of older cats. It is
claimed that the prevalence of the disease increased as
new household FRs have been introduced in the market.

While new FRs that are purported to be safer than their
“more toxic” predecessors are currently being used in
many materials, including the organobromine compounds,
polybrominated diphenyl ethers (PBDE) have been found
to act as endocrine disruptors. The compound was phased
out in the US in 2013.

However, the newer FRs may not be all that safe as the
ACS study included the PBDE alternative, organophosphate
esters FR. The cats in the study wearing silicone tags
showed elevated levels of TDCIPP. Cats and other pets
may also be exposed to FRs from other household
sources such as air fresheners, couches and mats.

Developing “greener” FRs

The use of additives has increased alongside the growth in
applications for such materials like plastics. Thus, proper
disposal of plastics not only is important in ensuring that
plastics do not cause pollution but also help keeping
potentially toxic substances from the environment.

Thus, manufacturers are also developing
“environmental friendly” FRs to address this concern.

One such development comes from Texas A&M
University’s new kind of FR coating developed using
renewable, non-toxic materials readily found in nature, such
as nanocellulose from wood and clay, according to a report
published in the Advanced Materials Interfaces journal.

The coating, the researchers reported, could provide
better fire protection to materials including upholstered
furniture, textiles and insulation. The uniqueness in this
current study lies in the use of two naturally occurring
nanomaterials, clay nanoplatelets and cellulose
nanofibrils, the researchers said. Prior to the study, the
materials have never been used to make a heat shielding
or FR coating as a multilayer thin film deposited from
water.

The coating offer is said to offer excellent oxygen
barrier to plastic films, commonly used for food
packaging, and better fire protection at a lower cost than
other, more toxic ingredients traditionally used in FR
treatments, say the researchers. Moreover, during the
flammability test, the coating showed that it can promote
insulating char formation and reduce the release of fumes
that feed a fire. The team says it is looking to developing
further the project for industry implementation.

Green alternatives come under fire

Meanwhile, a recent study by Germany’s University
Duisburg-Essen published in the Environmental Health
News (EHN) journal examined a new class of “green”
FRs typically used in foam insulation. It cited the PolyFR
butadiene styrene brominated copolymer manufactured
by Dow Chemical and said that when exposed to heat
and UV light, the compound breaks down into smaller,
possibly harmful chemicals like bromine.

In 2015, PolyFR marked the industry’s leap from
banned chemicals to safer alternatives, in line with
EU’s REACH Regulation on chemicals. German
chemical company BASF in 2014 switched to using
PolyFR in its PS-based insulation products from HBCD
(hexabromocyclododecane) FR, which was then
ruled to have persistent, bioaccumulative, and toxic
characteristics (PBT).

Dow has refuted this claim against PolyFR, stating
that it had conducted extensive testing on the safety
profile of PolyFR, including degradation. It said that it
“firmly believes this technology is a step in the right
direction to improve the sustainability” of FRs used in
PS foam insulation. The company also commented that
conclusions regarding the safety performance of the FR
“should only be drawn by studying conditions that are
fully relevant to the application itself”.

Though EHN has since updated its story, it still states
that PolyFR is a “regrettable substitution”. Lead German
researcher Christoph Koch has also since published a
separate study that concludes “rather limited” acute
toxicity. But even with Dow’s explanation, the publication
of the study has created doubt in the minds of many.

Progressing in recyclability of FRs

Meanwhile, another issue remains on FRs safe
degradation. A study by a team of environmental
scientists from the University of Massachusetts may
have just found a solution that is “technically simple
and environmentally friendly” to break down these
chemicals into “harmless” compounds.

The study has, for the first time, used a dynamic,
two-step process to completely degrade a common FR
chemical tetrabromobisohenol A (TBBPA), a brominated
compound, to carbon dioxide and water in water
treatment systems and in the natural environment,
using a special material called sulphidated nanoscale
zerovalent iron (S-nZVI).

The new method is an advancement from the usual
reduction or oxidation approach to remove TBBPA and
other organic refractory compounds that are difficult to
degrade.

TBBPA, which is added in finished articles, including
computer circuit boards and other electrical devices,
papers, textiles and plastics, is regarded as a PBT. It is
also suspected as carcinogenic and hormone disruptor,
and has also been detected in the environment, as well
as in animals and human milk and plasma

Added benefit to e-waste recycling

Plastics and other materials from electrical and
electronic device scraps make up the e-waste that is
posing challenges to recyclers, either that the materials
are hard to recycle or they contain ingredients that
break down to environmentally hazardous substances.
Tackling this issue of recyclability, the new additive
from Swiss speciality chemicals company Clariant
are fit for reuse while avoiding material performance
degradation.

The Exolit OP 1400 is phosphorus-based and halogenfree
additive, said to be a better viable option compared
to legacy brominated FRs, according to Clariant. Its use
is even more relevant considering the rise in demand for
PA66 engineering plastic, driven by industry trends such
as miniaturisation in electronic & electrical applications,
the shift to more lightweight materials in automotive and
by rising mobility demand.

Additionally, the Exolit OP maintains UL 94 V-0 rating
after recycling of production waste as verified by the
German institute Fraunhofer LBF. It confirms that PA6
and PA66 containing Clariant’s Exolit OP maintain the
rating also when recycled back into production streams
multiple times. This, Clariant said, is advantageous
both for the environment and manufacturers who are
keen to increase their use of production waste and postuse
recyclate in electrical, electronic and automotive
applications.

Another advantage is that Exolit OP is not subject
to Ecodesign application restrictions as outlined in
the EcoDesign Directive (2009/125/EC), a European
framework that aims to achieve the EU’s 2020
sustainability targets and provides criteria for electronic
displays that exclude halogenated FRs.

Picking out the real deal FR

In a related development, Clariant says it is safeguarding
its patent position in phosphinate-based FRs against
what it says are infringers. The company’s worldwide
intellectual property position related to phosphinate FR
products has not deterred some polymer compounders
and OEMs from obtaining a class of halogen-free FRs,
diethylphosphinate alu-minium salt (DEPAL)-based FRs,
from local Chinese suppliers.

These FRs, often combined with nitrogen containing
and inorganic synergists, have become workhorses in
engineering thermoplastics, mainly glass-filled nylons
and polyesters, but also epoxy resins, Clariant said. It
furthered that it has been developing and advancing this
technology for over two decades, so that its patented
Exolit OP FRs “have become the benchmark in quality
and performance for phosphinate FRs in the market”.

Clariant adds that it has more than 500 individual
patents or patent applications globally, including
in China, Japan, Germany, France, and the US, for
phosphinate-based FRs, related polymer compositions
and polymer products such as e.g., plug connectors,
circuit boards, encapsulating compounds, power plugs,
LED housings, capacitor housings, charging cables for
mobile phones, and engine covers.

New launches at the K2019 show

With standards in fire safety being raised across the
globe, demand for FRs is anticipated to increase and
may even surpass forecast values. By 2022, the FR
market is projected to corner US$10 million, according
to a report by Allied Market Research, which adds that
leading market players are introducing more advanced
additives to cater to the demand of end users, and for a
range of applications.

Thus, new additions are being rolled out. German
additives supplier BYK is offering an organophilic sheet
silicate for use in thermoplastics such as nylons. To be
showcased at the upcoming K2019 show in October, BYKMax
CT 4260 is the first product from the new group of
thermoplastic additives launched on the market under the
BYK-Max trade name.

It is especially suitable for use with halogen-free
FR thermoplastic compounds, since incorporating the
additive improves not only the FR properties but also the
dropping behaviour and crust formation, BYK said. In
return this new specialised additive also enables the filler
content, e.g., aluminium or magnesium hydroxide, to be
reduced. This leads to a significant improvement in the
process and physical properties and to a reduction in the
overall weight, adds BYK.

Also debuting its latest family of FR synergists at
the German show is South Korean specialty chemicals
company Songwon. Its new FRs are based on a proprietary
technology designed to combine high performance with
safety and sustainability, said the company. As the second
largest manufacturer of polymer stabilisers in the world,
Songwon will also be promoting its Sabo Stab UV216 light
stabiliser system developed for agricultural applications
by its long-time partner Sabo, an Italian manufacturer of
hindered amine light stabilisers (HALS).

Thus, it can be seen that creating a new league of FRs
that are non-toxic and not open to IP infringement still
remains a challenge for the industry.